Method for preparing colored rubber laminates

ABSTRACT

A COLORED RUBBER IS PREPARED BY STICKING TOGETHER VULCANIZED AND SEMI-VULCANIZED RUBBERS CONTAINING AN ETHYLENE-PROPYLENE RUBBER AND AN INORGANIC FILLER INTO WHICH A COLORING AND CROSS-LINKING AGENT HAS BEEN BLENDED, AND VULCANIZING THE RESULTING ASSEMBLY.

United States Patent Oflice 3,669,828 Patented June 13, 1972 US. Cl.161-252 6 Claims ABSTRACT OF THE DISCLOSURE A colored rubber is preparedby sticking together vulcanized and semi-vulcanized rubbers containingan ethylene-propylene rubber and an inorganic filler into which acoloring and cross-linking agent has been blended, and vulcanizing theresulting assembly.

The present invention relates to a process for producing a coloredrubber of ethylene-propylene. Particularly, the invention is concernedwith a process for producing a clearly colored rubber, which compriseproducing a colored composition of an ethylene-propylene rubber,sticking together a vulcanized rubber and a semi-vulcanized rubber ofsaid colored composition and vulcanizing the resulting assembly withoutmaking the vulcanized rubber get out of shape or subjecting it todeformation.

Rubbers prepared by blending natural rubber and synthetic rubber, forexample, styrene-butadiene rubber, polybutadiene rubber, etc. with aninorganic filler are poor in weather resistance and ozone resistance,and consequently, cracks are brought about on the rubber surface.Particularly, when an inorganic filler is employed, the results are notgood. Chloroprene rubber which is said to be relatively good in Weatherresistance as compared with natural rubber is effective only when afiller used is carbon black or an inorganic filler and black pigment areused together. However, colored rubbers other than black rubber, whichhave been prepared by using this chloroprene rubber, is markedlydiscolored due to ultraviolet rays, and it is believed that thisdiscoloration cannot absolutely be improved any more because of theessential efiiciency of the chloroprene rubber.

For imparting color patterns to natural rubber or synthetic rubbers, forexample, styrene-butadiene rubber and chloroprene rubber, it is usualmethod to apply color patterns to the rubber by abrasing the surface ofvulcanized rubber or sticking color patterns thereon using an adhesive.

Also, as the simplified method for imparting color patterns to therubber, there is employed a method which comprises coloring the surfaceof rubber with paints.

These methods, however, have such drawbacks that the adhesive to beemployed is expensive, and that the paints are apt to peel away from therubber surface, and consequently the rubber surface is markedly soiled.Accordingly, most of conventional rubber articles have been in blackcolor.

The ethylene-propylene rubber is excellent in weather resistance, ozoneresistance, thermal resistance and chemical resistance as compared withconventional natural rubber and other synthetic rubbers, for example,styrenebutadiene rubber, polybutadiene rubber, chloroprene rubber andthe like. Moreover, the ethylene-propylene rubber has clearness whencolored with pigments and dyes, and the rubber less in discoloring andfading can be obtained therefrom.

However, it has been diflicult to obtain manufactured goods of clearlycolored rubber because the ethylenepropylene rubber is poor inadhesivity and also on account of unavailability of excellent adhesivesbecause of non-polarity of the ethylene-propylene rubber.

The present inventors extensively studied a method for imparting colorpatterns to the rubber without using an adhesive, and as a result, theyhave attained the present invention.

The present invention is directed to a process for producing a coloredrubber having clearness and not being subject to getting out of shape ordeformation of the vulcanized rubber thereof by utilizing the fiatvulcanization property of a composition of the ethylene-propylene rubberblended with an inorganic filler, which comprises sticking together acolored vulcanized rubber of the said composition and rubber prepared bysemi-vulcanizing the said colored composition in such a manner that thesaid colored composition may not flow during vulcanization, andvulcanizing the resulting assembly.

The ethylene-propylene copolymer and theethylenepropylene-ternary-copolymer used in the present invention areproduced according to a well-known method using a catalyst well-known inthe field of the art to which the present invention pertains,particularly using a Ziegler- Natta type catalyst. Representativeexamples of the nonconjugated diene compound which constitutes anethylene-propylene-non-conjugated diene ternary copolymer include1,4-hexadiene, dicyclopentadiene, S-methylene-Z- norbornene,5-ethylidene-2-norbornene, 4,7,8,9-tetrahydroindene, and the like.

The ethylene-propylene rubber composition of the present invention isprepared by blending parts by weight of an ethylene-propylene rubberwith 50-300 parts by weight of an inorganic filler and a cross-linkingagent such as sulfur or an organic peroxide and further with a desiredcoloring agent, but, if necessary, the present composition may beblended with a process oil, a plastisizer and the like.

The inorganic filler which can be used in the present invention is anatural or synthetic inorganic filler. For example, it includes calciumcarbonates, clays, talcs, silica, silicates and oxides of titanium,zinc, aluminum, etc. The coloring is eifected by using organic dyes andpigments, and inorganic pigments, and these substances may be blended inamounts necessary for a desired color matching. When the amount of whiteinorganic filler to be blended is less than 50 parts by weight per 100parts by weight of the ethylene-propylene rubber, the reinforcing effectexpected becomes poor. On the contrary, when the amount of the inorganicfiller is more than 300 parts by weight, the filling thereof into therubber becomes difficult.

The cross-linking agent useful in the present invention includes organicperoxides, oxime compounds and sulfur. These substances may be usedalone or in combination. The organic peroxides to be used includedicumyl peroxide, 2,5-dimethyl-2,5-di(tert.-butylperoxy) hexylene andthe like. The oxime compounds include p-quinonedioxime, p,p'benzoylquinonedioxime and the like. When only sulfur is used as across-linking agent, the use of conventionally used vulcanizationaccelerator and activator becomes necessary therefor. However, saidsulfur blending agent is useful only for an ethylene-propylene ternarycopolymer.

The semi-vulcanization of the present invention can be effected bytreating the blend at a temperature of 200 C., preferably -160 C. for ashort period of time. The degree of semi-vulcanization is desirablywithin the range of 300-500% of weight increase rate after immersion ofthe semi-vulcanized rubber in benzene at 25 C. for 48 hours. Whenvulcanization proceeds over the above degree, no adhesion is attained oreven when adhered, the adhered surface bends to cause. deformation.Furthermore, if vulcanization is effected below the above degree, therubber flows when adhered and whereby the rubber puts out of shape, andthe desired object cannot be attained.

Weight increase rate is calculated on the basis of the followingequation.

Weight increase rate (percent) weight after swelling weight beforeswelling X 100 The adhesion method of the colored rubber sheet of thepresent invention is explained hereinafter. The aforesaid compositionobtained by kneading with an ordinary open roll or a Banbury mixer isextruded into any desired shape according to any of known method, forexample, using a calendar roll or an extruder and the extruded productis subjected respectively to semi-vulcanization and usualvulcanizatiomThe method for vulcanization is not particularly limited,and it can be effected at the heating temperature ranging from 120 to200 C. according to a compression molding using a heat press, directsteam vulcanization method using steam or indirect vulcanization methodusing hot air depending upon the shape of the article desired. The thusobtained vulcanized rubber and semi-vulcanized rubber are adhered byheating the two rubbers stuck together at a temperature ranging from 140to 200 C., preferably from 140 to 160 C. with a heat press.

The mold goods obtained according to the present invention haveexcellent adhesivity, coloring of any desired colors and exhibit precisecolor patterns, and whereby such products as could not be obtained fromconventional rubbers can be obtained simply.

Furthermore, the present products have excellent feature in Weatherresistance and ozone resistances, and therefore, they are suitable foruse in industrial accessories, automobile parts and the like articles.

The present invention is explained with reference to the followingexamples, but these examples are not given to limit the process of thepresent invention.

Furthermore, in all the following examples and reference examples, theozone resistance test was carried out using an ozone weather metermanufactured by Toyo Rika under the conditions of ozone concentration of60 pphm, elongation percent of 20%, and temperature of 50 C. The weatherresistance was determined using a weather tester (carbon arc type)manufactured by Shimazu Seisakusho under the conditions of elongationpercent of 20%, panel temperature of 60 C. and cycle of 18 min.rain-fall/2 hrs. The peeling-off test was conducted on a specimen havinga long rectangular form obtained by cutting a colored rubber sheet usingChoppers tipe tensile tester at a tension rate (180 peeling) of 500 mm.

EXAMPLE 1 The following composition A and B were produced using anethylene propylene-non-conjugated terniary copolymer (Royalene 301,produced by Uniroyal Co.) with use of a 8" roll for rubber. The blendingratios are all represented by part by weight.

Ethylene-propylene rubbein. 100 100 Stearic acid. 1 1 Zinc oxide. 5 5uri. 5 1. 5 Hard clay 80 80 Titanium dlX1d0. 35 Paratfinic oil l0 10Titanium nickel yellow (titanium yellow) 2. 0 Phthalocyauine Blue-B 3. 0Zinc dimethyldithiocarbamate 0. 75 0. 75 Tetramethylthiuram disulfide.0. 76 0. 75 Z-mercaptobenzothiazol 0. 0. 5

The following composition C and D were produced using natural rubber.

Composition C was vulcanized and thereby to prepare a sheet ofrectangular form. Subsequently, composition D was semi-vulcanized insuch a manner that the shape thereof may be able to pattern compositionC. Finally, the two compositions were stuck together and the resultingassembly was vulcanized.

Natural rubber (pale crepe) 100 Zinc oxide 40 40 Steario acid 1 1Titanium dioxide. 40 40 Wax 1 1 Sulfur 2. 5 2. 5 N-eyclohexylbenzothiazolsulphenamido 0. 5 0. 5 Phtlialocyanine Blue-B 3The adhesion strength, surface state, weather resistance and ozoneresistance determined respectively on 0-D compound rubber and A-Bcompound rubber obtained in Example 1 are shown in Table 1.

Furthermore, the natural rubbers were found to be difiicult to adhere toeach other because of difficulty in controlling the vulcanization rate,but such rubber which could be regarded as being adhered was tested.

TABLE 1 Ethylene-propylene rubber Natural rubber Adhesion strengthRubber surface Rubber surface ruptured. ruptured. Surface state ofvulcanized rubber- Clear color Unclear color shade. shade and zigzagged.Ozone resistance, time required for No change even 30 minutes.

occurrence of crack ,(60 p.p.h.m. after the lapse tongatiou 20%,temperature 50 of 2,000 hours. Weather tester (carbon are type), Nochange even 24 hours.

time required for occurrence of I after the lapse crack (20%elongation).

of 2,000 hours.

EXAMPLE 2 The following compositions E and F were produced from anethylene-propylene-non-conjugated diene ternary copolymer (Royalene 301,produced by Uniroyal Co.) using an 8" roll for rubber.

The blending ratios are all represented by part by weight.

Ethylene-propylene rubber 100 100 Stearic acid 1 1: Treated, complexaluminum silicate (Translink-37) 80 80 Titanium dioxide 35 Parafinic oil10 10 Titanium nickel yellow (titanium yellow) 2 Phthaloeyanii e green 3Dicumylperoxide (Di Cup 40 C) 7 0 7 0 Sultur 0. 3 0. 3 Zinc oxide 5. 05. 0

The specimen of composition E was vulcanized at C. for 10 minutes usinga hot press and thereby to prepare a circular sheet. Subsequently,composition F was semi-vulcanized at 160 C. for 5 minutes in such amanner that the shape thereof may be able to permit composition E bepatterned. Finally, the two compositions were stuck together and theresulting assembly was vulcanized at 160 C. for 30 minutes and therebyto obtain a colored rubber having clear color shade. I

Reference Example 2 The following compositions 'G and H were producedusing a chloroprene rubber. Composition G was vulcanized and thereby toprepare a circular sheet. Subsequently, composition H wassemi-vulcanized in such a manner that the shape thereof may be able tomake composition G be patterned. Finally, the two compositions werestuck together and the resulting assembly was vulcanized.

Chloroprene rubber 100 102 4 5 5 l 1 50 50 30 10 10 ax 2 2 StyrenatedphenoL- 1 1 2-mercaptoimidazoline 0. 5 0. 5 Phthalocyanine Blue-B 3 Theadhesion strength, surface state, weather resistance and ozoneresistance determined respectively on G-H compound rubber and E Fcompound rubber obtained in Example 2 are shown in Table 2.

Furthermore, the chloroprene rubber was also found to be difficult toadhere likewise in the case of the natural rubbers, but such rubber ascan be regarded as being adhered was tested.

TABLE 3 J-I compound rubber Adhesion strength Rubber surface ruptured.Surface state of vulcanized rubber Clear color shade.

Ozone resistance, time required for occurrence No change even after ofcrack (60 p.p.h.m., elongation 20%, temthe lapse of 2,000 perature 500.). hours.

Weather tester (carbon arc type), time required N 0 change even afterthe for occurrence of crack (elongation 20%). lapse of 2,000 hours.

EXAMPLE 4 K L M N Ethylene-propylene rubber (Royalene 301)... 100 100Paraflinic oil 10 10 30 30 Inorganic pigment (Tipaque TY70) 2. 0 2. 0Organic pigment (Cyanine Blue-HE) 3. 0 3. 0 Zine dimethyldlthiocarbamate0. 75 0. 75 0. 75 0. 75 Tetramethylthiuram disulfide... 0. 75 0. 75 0.75 0. 75 2-mercaptobenzothiazol 0. 5 0. 5 0. 5 0. 5

Compositions K and M were respectively vulcanized at 160 C. for 10minutes using a hot press and thereby to prepare the respective sheetsof rectangular form. Subsequently, compositions L and N wererespectively semivulcanized at 160 C. for 5 minutes in such a manner 2TABLE that the shapes of compositions L and N may be able g iomomprene35 to make compositions K and M be patterned.

F fil, rubber Finally,l compositionshK and L, and M and N wererespective y stuck toget er and the resulting assemblies R bb urf Rubbersurface Adhesion Stwngth ,i{,i ruptured. were respectively vulcanized at160 C. for 30 minutes Surface state of vulcanized rubber. Clear colorUnclear color Shade. Shade and 40 and thereby to obtarn the respectivecolored rubbers hav i at N h 56 5mm, ing clear shade.

Ozone resistance, t me require or o c ang'e even ours.

occurrence of amok (60 p'phm" after the lapse The adhesion strength,surface state, weather resistance eggrgation rate 20%, temperatureof2,000 hours. and ozone resistance of the respective colored rubbers 5Weather tester (carbon are type) No change even 100 hours. are Shown mTable Time required for occurrence of after the lapse crack (20%elongation). of 2,000 hours. TABLE 4 KL compound M-N compound rubberrubber EXAMPLE 3 Adhesion strength Rubbter slllace Rubbter star-face lllure 1'11 I8 The followmg composltlons I and I were produced from Surfacestate of vulcanized rubber. Clea? color Clea; color anethylene-propylene copolymer rubber (Dutral N/C., O t d Nshafiie.Nshalde.

- u zone resls ance, ime re uire oc an eeven oc an eeven Produced byMonte Edison usmg an 8 roll for foroccurenceofcrack (6 p.p.h.m., after te lapse after tlie lapse rubber. The blending ratios are all representedby part by elongation 20%, temperature of 2,000 hours. or2,0o0 hours.

weight.

occo

Composition I was vulcanized at 160 C. for 10 minutes using a hot pressand thereby to prepare a circular sheet. Subsequently, composition J wassemi-vulcanized at 160 C. for 5 minutes in such a manner that the shapethereof may be able to make composition ll be patterned. Finally, thetwo specimens were stuck together and the resulting assembly wasvulcanized at 160 C. for 30 min utes and thereby to obtain a coloredrubber having clear color shade. The adhesion strength, surface state,weather resistance and ozone resistance determined on the colored rubberare shown in Table 3.

N 0 change even after the lapse of 2,000 hours.

As is clear from the results mentioned-above, colored sheets obtained bythe process of the present invention are clearly printed and havesuperior adhesive strength. Thus, a rubber obtained in accordance withthe present invention is suitable for outer hoods for vehicles whichneed Weather resistance and ozone resistance as well as clear colortone.

We claim:

1. A process for producing a rubber article having clearly definedcolored areas comprising preparing a blend of ethylene-propylene rubber,inorganic filler, coloring agent and cross-linking agent,semi-vulcanizing said blend, preparing a second such blend andvulcanizing said second blend, thereafter laminating the saidsemivulcanized blend to the said second vulcanized blend, andvulcanizing the resulting assembly.

2. A process as in claim 1 in which the coloring agent in thesemi-vulcanized blend is different from the coloring agent in the secondblend, and the semi-vulcanized 8 blend is laminated in a desired patternto the second References Cited blend to produce a multitone assembly.UNITED STATES PATENTS 3. A process asm cla1m 1 1n whrch the semr-vul- I836 660 12/1931 Haertel 117 80 h 0 canlzed blend mcreases 1n welg t by 30 500% when 1m 2,308,724 H1943 Stamberger 161 240 mersed in benzene at25 C. for 48 hours. 5

4. A process as in claim 1 in which the amount of 2,838,854 9/1954Dosmann inorganic filler is fromySO to 300 parts per 100 parts by weightof ethylene pmpylene copolymen LELAND A. SEBASTIAN, Pnmary Exarmner 5. Aprocess as in claim 1 in which the ethylene- US. Cl. X.R. propylenerubber 1s ethylenepropylenenon-con ugated 10 diene terpolymer rubber.156--306, 308; 161-168; 26()-41 B 6. A colored laminate producedaccording to the method of claim 1.

